Embodiments of the present specification relate generally to magnetic resonance imaging (MRI) systems, and more particularly relate to a cryogenic cooling system and method for cooling superconducting magnets in the MRI systems.
A superconducting magnet is used to produce a magnetic field in MRI systems. In some MRI systems, an electric current from a power source is constantly applied to the superconducting magnet to produce and maintain the magnetic field. However, production of such a strong magnetic field entails a constant supply of the electric current in a range of hundreds of amperes. This constant supply of electric current to the superconducting magnet increases the running cost of the MRI system.
Furthermore, in certain other techniques, the superconducting magnet may be subjected to different heat loads in the MRI system. It is desirable to transfer these heat loads away from the superconducting unit to maintain the superconducting magnet at a cryogenic temperature and to operate the superconducting magnet in the superconducting state. Moreover, it is also desirable to optimally dissipate the heat from the superconducting magnet to transition the superconducting magnet from a normal state to the superconducting state without high boil-off of cryogen in the MRI system.
In a conventional MRI system, superconducting magnets/coils are housed in a helium vessel containing about 1500-2000 liters of liquid helium (He) to provide immersion cooling of the superconducting magnets/coils. Since this arrangement employs a large vessel with thousands of liters of liquid He, the arrangement is not only expensive to manufacture, but also cumbersome to transport and install at a desired location, such as, diagnostic centers. Additionally, delivery to remote locations of the refill of thousands of liters of liquid He may be inconvenient. Furthermore, conventional MRI magnet designs and their cooling arrangements may entail special installation requirements and high maintenance costs. In addition, installation of these systems in certain regions may be an onerous task. In other MRI magnet systems, the liquid helium is recondensed and hence to the loss of liquid helium to the environment is reduced. However, in these systems, the limited crycooler liquefaction power demands a very tight control of the thermal budget to ensure zero boil off.